Passive transponder identification and credit-card type transponder

ABSTRACT

A passive transponder identification system and credit card type transponder are disclosed, particularly, the transponder identification system to utilize a transmitting manner of two different RF signals is provided. The present invention directly relates to a passive transponder without any kind of power source. Therefore, the present invention has advantages of having a constant gain value by developing a high-gain dual polarizing antenna for a small credit card type passive transponder to identify at long distance, independently to any direction of the transponder; improving gain values than conventional transponder tag antenna by 6-9 dB to ensure a sub-permanent life time by providing the desired identification performance by a small credit card type passive transponder without power supply; and being applicable to any systems to identify and distinguish high-speed moving objects.

FIELD OF THE INVENTION

The present invention relates to a passive transponder identificationsystem operated by storage of information and transmission of inherentnumber and a credit card type transponder, and more particularly, to aradio frequency(“RF”) passive transponder useful in ID proximity card,pass card for bus or subway, and the like, which should recognize oridentify at close distance, simultaneously with IC card.

BACKGROUND OF THE RELATED ART

Such system requires remote-control transponder installed withsubminiature transmitter-receiver circuits capable of being carried inany moving objects therein. Particularly, the present invention providesa passive transponder to identification technique at relatively longrange and high-speed driving objects.

Conventional transponder identification system transmits a single radiofrequency to detect by antenna such as transponder tag, and non-linearimpedance of semiconductor diode used for this generates selectivelyhigh frequency(“HF”) of transmitted signals which is re-radiated to bedetected by receiving device. Such identification system has a shortageof practically not used due to occurrence of reading error at respondingto sensitivity and different conditions to ensure detection oftransponder within detection area.

It is importantly noticed that the transmitter-receiver circuit andelement thereof are non-linear and generate HF signal as well asfundamental transmitting frequency and results the signals input intothe receiver, even for transponder without non-linear impedance element.If sensitivity of the receiver is lowered to reduce the effect ofharmonics directly radiated, weak-energy harmonics re-radiated by thepassive transponder element will be absorbed in the former and not reachto the receiver. Of course, such problem may be minimized by ideallyshielding the transmitter and the receiver and/or by means of RFFiltering circuit. However, the filter has a problem of causing evensmall frequency shift of the transmitted signals to easily serve asre-radiation frequency present outside of the filter pass-band, thusrequiring very sophisticated shielding capability. Furthermore,frequency shift may be resulted from Doppler effect occurred in thetransponder moving at high speed within the detection area. While theseharmonic signals easily transmitting to the outside cause undesired datainformation to be radiated from any transponder beyond the detectionarea.

Consequently, HF energy which transmits by unexpected reflection such asmulti-stationary wave is not effective to accomplish the originalpurpose of the system.

On the contrary, if insufficient amount of energy is received orre-radiated by harmonics, the system may not respond even thetransponder element being actually present, within the detection area.For example, such condition may happen when antenna of the transponderantenna is unsuitably orientating corresponding to transmission field oris electro-magnetically blocked from receiver by nearby vehicles,partition wall on road, interception bar of toll gate and so on. Also,in case the transponder coming close to human body or metallic objects,it deflects tuning of a resonant tank circuit to result the dissipationof HF energy required by receiver. Although the transponder may beconstructed to control frequency response from the receiver so tocompensate frequency alteration by means of signal tracking circuit, thework efficiency of the transponder is decreased whenever the tuning tankcircuit is run at any frequency other than normal one.

Alternatively, as a solution to overcome the problem to restrict HFtransmission within the detection area in which non-linear impedanceelement acting as a signal mixer to generate summed or subtractedfrequency between both transmitting signals having different frequencieseach other is present, double field system using low frequency (“LF”)electro-statistic field formed between discontinuous conductors arrangedopposite to the HF electro-magnetic field and the detection area isadaptable. The non-linear impedance element applied to such two fieldsserves often as a mixer to generate summed or subtracted frequency to bere-radiated to the receiver.

However, even though power consumed in the detection area is importantto form electro-statistic field required within the detection area, suchfield may be unfortunately prevented from the transponder by conductorenclosing it or conversed from the transponder by traffic signs made ofmetallic materials or other metal structures around.

In addition, LF field is likely to be under reading error or immobilecondition at long distance by nearby metal structures.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a passive transponderidentification system, in particular, a transponder identificationsystem utilizing a manner for transmitting two different RF signals,that substantially obviates one or more problems due to limitations anddisadvantages of the related art.

An object of the present invention is to make either of such RF signalsto be tone-modulated and received by the passive transponder, theresulted signal being mixed through non-linear impedance to bere-radiated at the same high frequency with the sum frequency of both RFsignals and identified by means of narrow-bandwidth receiver.

The invention directly relates to a passive transponder having no kindof power supply.

Another object of the present invention is to provide a passivetransponder including non-linear impedance element such as semiconductorIC (integrated circuit), for example, a tag used in any identificationsystem for mobile objects such as vehicles, the transponder beingconnected to a micro strip antenna shifted toward both sides of theselected center frequency.

Such non-linear impedance element connects both sides of closed looparea at one end of the antenna in order to form a tuning tank circuithaving a frequency higher than the selected frequency by 2 times as theresonant frequency thereof.

Further, the first transmitter generates tone-modulated high frequencybiased or polarized to one side of the center frequency while the secondtransmitter generates continuous wave(CW) high frequency polarized tothe other side of the center frequency. Such both signals areindependently and suddenly turned to dipole antenna strips perpendicularto each other arranged to cover desired area. The said dipole strips arealigned at a right angle to each side at individual frequencies, and, atthe same frequency, positioned perpendicular to the opposite side.Therefore, it is resulted that cross-polarized transmission issuccessfully performed at both frequencies within the requisitedetection area.

Two different frequencies received by the passive transponder iscombined by means of non-linear impedance element. The tank circuitresonates to a single high frequency identical to sum of such twofrequencies and 2 times higher than the center frequency. The generatedresonant frequency is re-radiated to be identified by the interrogator.This is detected by super narrow-bandwidth receiver in which datainformation produced and loaded in the passive transponder responds tothe sum frequency.

The modulated tone including data signals introduced from the passivetransponder creates charges progressively increasing from the receivingsignal, in order to compare it with reference level pre-set to outputthe received data code in a certain interval only when the signaldetected has sufficient signal intensity and continuous time.

The present invention relates to an interrogator and a transponderidentification system, especially, more improved passive identificationsystem utilizing non-linear impedance semiconductor element connected toany printed dielectric micro-strip antenna attached to objects such asfront glass or license number plate, parcels, patient in hospital,animals, credit card and the like, which requires monitoring andidentification. The system has information stored in digital manner.

In another aspect of the present invention, a system to detect cars orother objects existing within the detection area includes a transmitter100 to radiate two RF signals having different frequencies in said areafrom a transmission antenna 110, either of the signals being modulatedto a certain LF, and alternative antenna 210 tuning to two differentcenter frequencies, wherein a non-linear impedance semiconductor circuitpart 220 inserted into said antenna 210 combines both RFs, and thesystem further comprises a narrow-bandwidth receiver 300 including areceiving antenna 310 which tunes data tone, re-radiates it to thecombined frequency, excludes RF signal and harmonics to detect themodulated signal of two frequencies, and receives and demodulates themodulated signal.

One of such RF signals transmitted is the tone modulated high frequencyf1 and the other is the continuous wave from the fixed RF f2(non-modulated CW). LF modulation results continuous tone-modulated RFsignals and restricts them within a defined frequency range.

Such both different harmonics signals are transmitted from a dielectricdipole transmission antenna 110 to a detection area, one of them f2being oscillated from high stability alteration oscillator 111 at fixedfrequency (i.e., 905 MHz) toward CW, as shown in FIG. 5. Said signal ispolarized from the center frequency by about 1%. The other one f1 is thetone-modulated signal ranged of 1-25 kHz to form high frequency signalsbiased by ±5 kHz from carrier frequency. The high frequency of 925 kHzis made by VCO (Votage Controlled Oscillator) 112 illustrated in FIG. 4.Both frequencies are uniformly polarized by the center frequencyselected. As a result, a mean center frequency of such signals is equalto the selected center frequency.

The tone-modulated signal f1 controls the occurrence of stationary wavecausing blind spot within an area detected by the passive transponder200.

Such transponder 200 comprises charge pump circuits 230, the passivedielectric substrate folded dipole antenna 210 and the non-linearimpedance semiconductor circuit part 220, the charge pump circuits 230being connected to a longitudinal part placed in a space surrounded byclose loop area faced each other to provide a tank circuit to tune withthe second harmonics resonant frequency. Such charge pump circuit 230consists of a capacitor and an inductance. Alternatively, the non-linearimpedance circuit part 220 consists of a non-linear impedancesemiconductor 220A, a Schottky diode D and condensers C1, C2 and a powersupply part equipped inside such semiconductor 220A.

Said narrow-bandwidth receiver 300 is, as illustrated in FIG. 6,comprises a carrier signal receiving antenna 310, a filter 311 tointercept all signals other than the narrow-bandwidth signal created bythe resonant frequency of said transponder 200, a demodulator in whichdetection of signal widths is performed to compare together widths ofthe receiving signals filtered and to detect said LF modulation onlywhen over the preset reference level, and respond depending on theresult of comparison-determination by a comparator 312. In this regards,“detection” means detection of LF modulation. The detection function isapplied to the digital data signals overlapped by the narrow-bandwidthreceiver 300 as a means to initiate the pre-determined digital stream sothat it indicates the passive transponder 200 existing within thedetection area whenever the intensity or duration of signals which wereproduced in the transponder 200 and detected by the narrow-bandwidthreceiver 300 exceed lower limits thereof preset.

Moreover, said receiver 300 includes a band pass filter 311 to preventsignals except the one within the narrow-bandwidth received by thereceiving antenna 310 and generated in the resonant circuit of thetransponder, a series of means consisting of a local oscillator 314 toproduce intermediate frequency IF for demodulating signals within thepass-band of said filter 311, multipliers 315,316, filters 317,318 and amixer 319, an amplifier 320 to amplify said the IF signal, alternativeamplifiers 321,322 to compare and determine width of IF, a comparator312 to generate LF signal only when the width of comparison-outputexceeds a pre-determined threshold, and a discriminator 323 to correctthe narrow-bandwidth which responds depending on thecomparison-determination output to demodulate said IF. The above LFsignal is one of RF signals within a narrow range of frequency deviationlimit which forms a constant tone modulation. Said narrow-bandwidthreceiver 300 can accept a phase locked telecommunication way by VOC 327to tune with said constant tone frequency and activate an amplifier 340connected to the output in order to allow digital data stream to run fora constant period.

In a further aspect of the present invention, the system to detect thepassive transponder 200 being within the detection area comprises atransmitter 100 existing within the detection area to produce andradiate narrow-bandwidth RF as a carrier frequency modulated by theconstant LF tone. The transponder 200 responding to a frequency signalfrom the transmitter 100 can be radiated by said transmitter 100 inorder to generate and re-radiate a carrier signal by using differentharmonics; the signal re-radiated capable of forming fixed LF tone. Thereceiver system 300 consists of the narrow-bandwidth filter 311 to blockthe carrier signal re-radiated by said harmonics in order to produceoutput filtered responding to the re-radiated signal received by theantenna 310 which receives such re-radiated carrier signal and thesignal received by the antenna 310 even to the frequency not limited tothe narrow-bandwidth frequency; and a demodulating means responding tooutput comparison level, the means allowing the LF signal to be createdand demodulating said filtered output only when the comparator 312 actsexceeding the pre-determined threshold value.

On the above, such receiver system has several demodulating meansresponding to the observation on said LF modulation signal to activateoutput for minimum time after the observation initiates. Thenarrow-bandwidth RF signal consists a stable carrier modulated by afixed audio-tone. The narrow-bandwidth filter 311 includes a localoscillator 314, a mixer 319 to create IF signal and a correction filter324 signaling IF; two or more means to perform comparison-determinationwithin the pass-band by detecting width thereof and to amplify IFsignals to demodulate signal from the correction filter, saiddemodulation means corresponding to widths of output from suchcorrection filter 324. The demodulation means comprises a clamp circuit325 responding to the comparison-determination function to fix output ofa narrow-bandwidth RF discriminating device and a correctiondiscriminator 323 so that a fixed-tone demodulation signal develops atoccurring output. Such comparison-determination by the comparator 312passes through when the determined value exceeds the threshold value.

In addition, such demodulation means of the receiving system 300activates digital data stream output for a constant time period; thedigital data code stream being ranged from 64 bits to 16 kilobitsdependent to a memory circuit 220A (semiconductor) attached inside thetransponder 200. FIG. 6 shows a data detector 328, a bit error detector342 and a low-pass filter 342.

In such construction of the system as described above, an elongatedantenna zone extending over the non-linear impedance circuit part 220for the second harmonics (for this invention, 1830 kHz) and the chargepump circuit 230 is approximately λ/4 relative to the selected centerfrequency (for the present case, 915 kHz), as shown in FIG. 3; thecircuit part 220 being determined by the capacitance of semiconductor220A and the inductance of the close-loop area adjacent to the antenna210 and the circuit part 220.

FIG. 3 illustrates an impedance of transmission line Z of 500 ohms andHF rectified DC current flows I1, I2. A short-circuit diode D providesthe rectified current given by f1, f2 into a power supply part of suchsemiconductor 220A to carry out mixing+frequency doubling+data streamadding processes to send the rectified current toward the receiver. Thesemiconductor 220A is loaded with data by the power of charge pumpf1(mod)+f2 formed by means of such short-circuit detection diode D.

It is more important that an operation method to use both frequenciescan reduce drifting effect of a transmitting frequency and increasebandwidth of the system in the efficiency aspect of the transponder forre-radiating an incident HF signal of a Back scatter. Particularly, thefrequency tuned with antenna 210 of the transponder 200 can be presentin any location between two frequencies transmitted without excessivereduction of the efficiency of said transponder; thus, it needs no useof accurate antenna to be manufactured while problems relatingnon-tuning could be reduced to a minimum. In this regard, common tuningpoint of the transponder 200 is polarized toward the lower side of twofrequencies due to dielectric loading effect of any object adjacent tothe transponder. For example, if it was re-tuned downward the selectedcenter frequency of said antenna of the transponder 200, it couldincrease the efficiency of the transponder 200 relative to anytransmitting frequency lower than it. The entire mixer is not seriouslyinfluenced by this condition because the desired mixing performance isdeveloped by 10 or more of HF power ratio. Therefore, the driftingeffect of the transmitter is minimized by such manner described above.In other words, unlikely the harmonics re-radiated in a single frequencysystem, the shift in frequency of the transmitter is not multiplied andthe drift at one frequency can be offset by the opposite shift of theother transmitter.

Re-radiated signal of the transponder 200 has an intensity and frequencystability sufficient to remove dual-identification error possible incooperation with a collision-avoidance software of correspondingreceiver and provide the maximum sensitivity and the minimum bandwidthof the receiver. Such re-radiated signal passes through very narrowband-pass filter to intercept the transmitting frequency into theantenna 310 receiving circular polarization; the received signal beingamplified by normal demodulation techniques to produce modulation datatone. In general, audio-tone (i.e., 2 kHz) is available to modulate RFcarrier wave to apply a signal (i.e., 1808.5 kHz) from a stable localoscillator 314 to a passive mixer receiving input signal, so that itmakes signal filtered and amplified from the antenna 310 of saidreceiver to create preferable IF (i.e., 21.5 kHz) at output of the mixer319. IF output from the mixer 319 is amplified by an amplifier 320,subsequently passes a narrow band-pass filter 324 (i.e., 30 kHz)defining a pre-detection bandwidth and a correction discriminator 323 tocarry out discrimination performance; and is clamped by a clamp circuit325 until it has an intensity sufficient to create voltage(potential) ofAGC detector 326 in excess of reference level set up for determining thesensitivity of system. Then, by opening the clamp circuit 325, VCO 327is applied to PLL/Data-tone detection circuit (consisted of VCO 327 andFree amble detection circuit 313) having a free running frequency equalto data-tone and capable of gaining a stable data-tone within a narrowrange of frequency such as ±10%. If loop gets the data-tone, arectangular detector acquires digital information from CPU andtransferred into a phase locked state to output the received transponderdata information having continuance ability sufficient to be stored.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention.

The objectives and other advantages of the invention may be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings;

FIG. 1 is a block diagram schematically illustrating the entireconstruction of an interrogator and a transponder of the presentinvention;

FIG. 2 is a concept drawing illustrating the mechanism to radiate twodifferent RF frequencies in said interrogator and to re-radiate theadded frequency thereof in said transponder;

FIG. 3 a is a block diagram schematically illustrating performance ofthe transponder of the present invention;

FIG. 3 b is a construction drawing practically showing non-linearimpedance semiconductor circuit part of the present invention;

FIG. 4 is a flow chart illustrating signal stream of a transmitterhaving modulated tone as shown in FIG. 1 in functional roles of partsthereof;

FIG. 5 is a flow chart illustrating signal stream of alternativetransmitter having continuous wave as shown in FIG. 1 in functionalroles of parts thereof;

FIG. 6 is a flow chart illustrating signal stream of a receiver havingmodulated data as shown in FIG. 1 in functional roles of parts thereof;

FIG. 7 a is a front and standard view illustrating outward appearance ofa conventional credit card;

FIG. 7 b is a side view of such credit card shown in FIG. 7 a;

FIG. 8 a illustrates a block planning drawing of high-gain antenna ofthe present invention to be arranged into a credit card;

FIG. 8 b is a cross-sectional view illustrating the manufacturingprocess of remote identification credit card available in the presentinvention;

FIG. 9 illustrates a constructional drawing of a high-gain antenna ofthe present invention;

FIG. 10 illustrates a constructional drawing of alternative principleantenna;

FIG. 11 is another cross-sectional view illustrating the antenna of thepresent invention in its constructional parts;

FIG. 12 illustrates a comparative graph corresponding to directions ofthe antenna;

FIG. 13 is a block diagram schematically illustrating automatic tollgatesystem utilizing a remote RFID built-in credit card according to thepresent invention;

FIGS. 14 a, 14 b and 14 c are drawings partially illustrating vehiclesequipped with such RFID credit card o shown in FIG. 13 according to thepresent invention;

FIG. 15 a is a plan view illustrating the direction of RF signal streamand the identification area in such tollgate structure according to thepresent invention; and

FIG. 15 b is a front view illustrating same as shown in FIG. 15 a.

[Numerical Description of Main Components]  10: credit card 11: magneticband  31: card clip 32: card holding stand  33: card pocket 40:interrogator  41: identification processing computer  42: charging andmanagement computer  43: central computer  45: plate numberphotographing system (video system)  46: financial information computernetwork (VAN) 100: transmitter 110: transmitting antenna 200:transponder 210: dielectric folded dipole antenna (metal antenna) 211:dipole resonant antenna 212: slot antenna 213: data slot antenna 220:non-linear impedance semiconductor circuit 230: charge pump circuit 300:narrow bandwidth 310: receiving antenna 311: filter 313: free ambledetecting circuit 314: local oscillator 319: mixer 323: correctiondiscriminator 325: clamp circuit 328: data detector

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

[Example 1]

In this example as an embodiment of the present invention, a credit cardtype transponder is equipped with RF Remote Identification System(“RFID”) using RF to identify at long distance.

More particularly, the system utilizes the open area of a micro-stripantenna to a maximum and accomplishes the greatest radiation efficiencyby properly arranging two slots and two dipole antennas and matching theresonant point relative to the secondary harmonics of the received wave;and receives beam power radiated from an interrogator to the highestdegree within a small size of card so that it can eliminates the lowefficiency problem of conventional system which uses Back Scatter havingthe same transmitting/receiving frequencies as its carrier;characterized in that it consists of dual-polarization antenna formed byarranging said two slot resonant antennas perpendicular to each other toconstantly manage the accepted power dependent on the direction ofantennas and to ensure remote identification performance.

This system is usually divided into a passive type transponder systemwhich receives Beacon transmitted from the interrogator, converses highfrequency(“HF”) of the Beacon into DC power source to run logic andmemory semiconductor, then, modulate and transmit inherent informationinto such Back Scatter; and a semi-passive and/or active typetransponder system which uses alternative power supply at a tag of thetransponder part as the working power for the memory semiconductor.

In general, such transponder system is widely used in any short-distanceapplications such as subway and/or bus pass card, ID proximity card,parking lot and automobile control system with a built-in battery,animal caring system, warehousing management system and is on theincrease of demand for application. Also, various type antennas areused; for example, a small tag type antenna in using at a certainadjacent distance and a coil type loop antenna for LF, while being undera process of high frequency (HF), the antenna is such a micro strip ordipole antenna type having its gain ranged from −3 to +3 dBi and usingthe linear type antenna for polarizing side.

The HF passive transmitting/receiving system to identify ones personalidentity by means of Back Scatter has a restriction that it has no morethan about 5 meters as the upper limit of identification distance, inspite of its benefit to be applicable in various applications, so thatthe known passive system is insufficient and has limitations such as thereduction of identification range and the lowered identification rate,etc.

In order to apply the system to high-speed object, it may possible toutilize active type transmitting/receiving system or semi-active typeone with a built-in battery or alternative power supply to identifyhigh-speed object or object at a long distance, such as OBU (On BoardUnit) taking charge of RF telecommunication part.

Such active or OBU types are limited to its application due to thedifficult problem in connection with miniaturization (size-reduction) ofthe transmitting/receiving system; not ensure the durability againstdeterioration of the active elements; and, in particular, although thesystem is able to be reduced its size by using the battery for clock,the problems involving durability or stability of battery and shorteningof life time thereof still exist since the life time of battery isdirectly influenced by such identification distance or number of timesto be used.

In addition, the system with a built-in battery is impossible to bemanufactured into any kind of credit cards. Further, since antenna ofthe transmitting/receiving system equipped with the battery is of linearpattern to use straight-polarization, its alteration of gain remarkablyincreases dependent on the relative direction of transponder tointerrogator to cause the identification distance being reduced asanother difficult problem.

The present invention is proposed to solve the above-mentionedinconvenience.

An object of the present invention is to provide a system to utilize theopen area of a micro-strip antenna to a maximum and to accomplish thegreatest radiation efficiency by properly arranging two slots and twodipole antennas and matching the resonant point relative to thesecondary harmonics of the received wave; wherein said system receivesbeam power radiated from an interrogator to the highest degree within asmall size of card so that it can eliminates the low efficiency problemof conventional system which uses Back Scatter having the sametransmitting/receiving frequencies as its carrier; characterized in thatit consists of dual-polarization antenna formed by arranging said twoslot-resonant antennas perpendicular to each other to constantly managethe accepted power dependent on the direction of antennas and to ensureremote identification performance.

Consequently, the present invention is characterized in that the antennais designed and manufactured by covering both sides of the copper ofaluminum thin plate with PVC material and applying a micro strip andslot-resonant circuit to the PVC covered plate to result a credit cardtype product.

Practically, with regard to the design and manufacture of antenna forthe transponder card, it comprises a metal antenna combined of taperedslot antenna, dipole antenna and integrated circuit; comprising toarrange two tapered slot antennas perpendicular to each other to formdual-polarization in consideration with voluntary orientation to handleand place the credit card; to widen the open area enough to match withthe size of credit card to increase the receiving HF power to itsmaximum degree; to position two dipole antennas to increase thetransmission gain; further, in order to accept the information marked byembossing at issuing the credit card, to make both sides of the copperthin plate of 0.1 mm or less thickness to be matched with the dielectricconstant value of PVC materials covering the copper plate.

As mentioned above, the present invention relates a passive typetransponder to identify objects by means of a mechanism comprisingtransmitting Beacon from an interrogator and conversing the received HFBeacon into DC power source to activate logic and memory semiconductorto modulate and transmit inherent information to Back scatter.

Conventional credit card, as shown in FIG. 7 a, having a dimension of85.6±0.12 mm (A)×53.98±0.55 mm (B) and consisted of a magnetic band 11having min. 5.54 mm (C) and max. 15.82 (D). A passive transponder of thepresent invention is inserted into to an existing credit card 10 havinga thickness of 0.76±0.08 mm (E) as illustrated in FIG. 8 a. In thisregard, a dielectric folded dipole antenna (made of metal material) 210of the transponder should direct faced to the magnetic band 11 at itsimaginary contact surface and be located on lower part of the card 10 toallow sufficient amount of electromagnetic beam to be generated at theopen side of the slot.

Moreover, a non-linear impedance semiconductor circuit part (integratedcircuit: IC) for the transponder, as shown in FIG. 8 b as side view ofthe credit card 10, is arranged between min. 14 mm (F) and max. 19 mm(G) apart form edges of and within the card made of PVC materials,together with thin plate-shaped antenna 210, as shown in FIG. 8 a, sothat it prevents the effect of character embossing on the credit card10.

Alternatively, FIGS. 9 and 10 show the structure of antenna 10 insertedinto the credit card 10. The passive transponder 200 is power suppliedby RF bandwidth of an interrogator (not shown) and the power beingrequired to activate the semiconductor circuit part 220; and consumesthe energy to transmit response code by the antenna 210 and othernon-linear elements impedance modulation; is constructed of antenna 210and at least one of semiconductor circuit part 220, the construction andfeatures of the antenna 210 being defined by physical and/or chemicalproperties or action-demanding frequency of the materials enclosing thetransponder.

In other words, as illustrated in FIGS. 9 and 10, the HF RFIDtransponder of 400 MHz-25 GHz is built in the credit card 10 to use itas a general credit card, as well as applies conveniently in varioussystems such as tollgate or toll road charging system, gas stationaccounting system, parking lot charging and management system and thelike, without connecting to alternative telecommunication apparatus.

A slot antenna 212 having a thin plate shaped slot structure useful in400-25 GHz HF RFID and an antenna 211 having dipole structure and, inaddition to, the circuit part 220 placed at center part of the slot areequipped within PVC material at wider side of the card 10 and/or variousID proximity card relative to the magnetic band 11, as shown in FIGS. 8a, 8 b.

And, FIG. 11 shows an antenna inserted into the credit card 10. Theantenna is made of copper thin plate or other similar conductivematerials to construct a slot antenna 212 corresponding to λ/4wavelength at center part thereof; and to form horn shaped tapered slotantenna 213.

Besides, as shown in FIG. 9, in order to increase transmission gain andreduce or substantially eliminate orientation problem of the antenna,two slot antennas 212 are arranged at right angle to form dualpolarization and constructs twp dipole resonant antenna 211.

Such constructed, for example, 915 or 2.45 GHz transponder preferablycomprises a linear dipole or folded dipole to absorb plenty of energyand to power supply and respond semiconductor circuit 220.

An important component of said super HF RFID transponder is antenna 210.In case of transponder running at high frequency (400 MHz-25 GHmz) themost important properties are orientation and bandwidth of the antenna;and it usually depends on gains of half- or multiple half-wavelengthdipole antenna.

General micro strip dipole antenna has very low radiation-resistance toresult low efficiency which is inadequate to form credit card, althoughit is overcome by using relatively thick plate.

Therefore, an embodiment of the present invention is a tapered slotantenna suitable to a remote RFID transponder metal antenna 210 equippedinside a credit card.

Such metal antenna 210 is fully flat and has end-fire pattern; provideshigh orientation and bandwidth; is practically prepared by a thin plate;shows good radiation pattern and radiation gain; and reduces functionalloss by TMO surface wave.

Also, said tapered slot antenna 213 is a horn shaped antenna having slotwidth progressively extended in steps and radiates electro-magnetic waveparallel to side of the antenna.

Since the structure of such antenna 213 is similar to the slot line, thecontact area thereof is located onto the micro strip line.

Therefore, as the antenna can be simply integrated with any feeder andconformity circuit it is preferably used as a broad-bandwidth antennaelement for the remote identification HF transmitting/receiving system.

Receiving power of the antenna is proportional to area as a gaincalculation formula applied to micro strip antenna;

By arranging two slot antennas 212 perpendicular to each other, asillustrated in FIG. 12 as a comparative graph for orientation, it canovercome the orientation trouble; and at both end sides thereofcomprises two dipole antennas 211 to complete a resonant circuit toobtain maximum gain.

[Example 2]

In this example as another embodiment of the present invention, anelectronic fare collection system for driving automobiles such as tollroad charging system (referring hereinafter “charging system”) using aremote RFID built-in credit card (referring hereinafter “RFID creditcard”) prepared by Example 1.

FIG. 13 illustrates a systematic drawing of the charging system usingRFID credit card 10, the charging system being consisted of aninterrogator 40 to directly identify the RFID credit card 10 placedwithin the driving automobile without any kind of automobile loadingmeans; a detector 44 to detect and sort type of the automobile; a videosystem 45 to photograph plate number of illegally passing car; and anidentification and control computer 41 to identify the RFID credit cardof the automobile passing the tollgate. The system further includes aknown management computer 42 to collect fare to receive data transmittedby the identification computer 41, a central computer 43 and a financialinformation computer network (VAN) 46.

In order to show intention to pay the fare, an user can insert or holdthe RFID credit card 10 on a card holding stand 32 and place it on thedashboard of car (as shown in FIG. 14 b), install a card clip 31 made ofPVC material behind the room mirror (as shown in FIG. 14 a) or insertthe card into a card pocket 33 made of clear vinyl material.

Additionally, said RFID interrogator 40 is positioned in a level of 4.5m from the road ground at upper center part thereof, and a camera 45 aof the video system 45 is located at the same level but 20 m backwardfrom it; and at cross road both of them being arranged to Beaconorientation opposite to each other to reduce mutual interference to aminimum degree.

Such construction of the present invention can transmit Beacon togetherwith question at the interrogator 40; encode the card inherent numberand information of the entered car and respond to it by means of RFIDcredit card 10 acting with the power of Beacon when a car placed withRFID credit card 10 is entering to the Beacon area; read the cardinherent number and information transmitted from the RFID credit card 10by means of interrogator 40 then send the read data to the computer 41.The computer 41 receives information relating type of the cartransmitted by the detector 44 to detect and sort type of the car,calculates fare of the corresponding car, passes the informationidentified of the credit card through the known management computer 42and the central computer 43 and asks usage approval to particularcapital firm corresponding to the card.

If “Disable” result accepted from the capital firm, any alarm lamp orother output device immediately indicates the result to the user. Also,in case of the detection result being identified from the detector 44without identification of RFID credit card 10, the car is classified asan illegally passing car, alternatively, in addition to indicate“Disable” for the card.

The management computer 42 collects corresponding information to finepenalty by every cars from the identification computer 41 and managesit; asks usage approval of card to a CPU connected with the managementcomputer 42; searches a database including “disable” cards and transmitsthe searched result to VAN 46. The central computer 43 manages andcontrols penalty fining information and billing information to capitalfirms and is connected to capital firms through VAN 46.

In order to efficiently identify RFID credit card 10, it is possible toset card clip 31 made of PVC material on beyond the room mirror (asshown in FIG. 14 a) or make and set a card holding stand 32 on thedashboard of car (as shown in FIG. 14 b) to easily recognized from frontside of the car. Or a card pocket 33 made of clear vinyl material (asshown in FIG. 14 c) is attached to a desired location on the front glassof car to hold RFID credit card 10 and show intention to pay the fare.

The interrogator 40 and the video camera 45 a to identify RFID creditcard 10 placed in the driving car is arranged as illustrated in FIG. 15a. Identifying areas located in opposite directions of both road arecrossing each other. The interrogator 40, as shown in FIG. 15 b, islocated on a level at center of the road to allow cars includinglarge-sized vehicles able to pass through to form an effective system.

As another embodiment of the present invention, it will be understoodthat the present invention is applicable to automatic charging systemsfor parking lot and/or gas station comprises a remote RFID interrogator40 to directly identify RFID card 10 in car which is not to be construedas limiting the present invention within the sprit and/or scope of theclaims.

The present invention was developed as a solution to overcome theexisting problems in connection with restricted identification range,errors caused by frequency shift resulted from Doppler effect occurredin the transponder moving at high speed within the detection area. Also,the present invention can be applicable to moving objects identificationsystems for long or short distance such tollgate charging system.

The present invention has advantages of having a constant gain value bydeveloping a high-gain dual polarizing antenna for a small credit cardtype passive transponder to identify at long distance, independently toany direction of the transponder; improving gain values thanconventional transponder tag antenna by 6-9 dB to ensure a sub-permanentlife time by providing the desired identification performance by meansof a small credit card type passive transponder without power supply;and being applicable to any systems to identify and distinguishhigh-speed moving objects. It will be appreciated that the presentinvention can be used in various applications such as tollgate chargingsystem, parking management system, admission(entrance and exit)management system, automatic member identification and managementsystems of gas station and the like by the improvement of passivetransponder techniques and appearance of various applicable systemsaccording to the present invention.

Particularly, the present invention provides the performance to chargetollgate (or toll road) fare by using a credit card installed with RFIDfunction, which enables smoother and faster traffic stream than priorknown manual charging or mechanical charging systems by about 4 times.Also, the inventive system has a communication speed equal to that oneof a way using car loading device previously used in advanced countriesbut is more preferable in the economical aspect thereof since it needsnot the high-priced loading device about 40 times of card price. Ofcourse, it requires no purchase of the car loading device.

The inventive RFID credit card can be provided as a substitute for theexisting one by capital firms, thus, lead to rapid distribution of theelectro-charging system. Therefore, the present invention can saveenormous operating expenditure because it eliminates the requirement of3.5 human labors per road caused by using previous manual chargingsystems under bad working conditions such as smoke, safety problems andso on, in addition to, reduce excessive opportunity loss, storage andtraffic costs by reducing stopping time of cars at the tollgate ifquickly spreading the present invented systems.

Among other applications, the present invention is efficiently utilizedin such as auto-identifying and paying system, management and chargingsystem and the like useful for parking lot.

The forgoing embodiments are merely exemplary and are not to beconstrued as limiting the present invention. The present teachings canbe readily applied to other types of apparatuses. The description of thepresent invention is intended to be illustrative, and not to limit thescope of the claims. Many alternatives, modifications, and variationswill be apparent to those skilled in the art.

1. A passive transponder identification system for detecting andmonitoring the existing of automobiles and other object within aconstant detection area comprising a transmitter 100 to radiate twodifferent radio frequency (RF) signals within the area to a transmittingantenna 110, either of the signals being modulated to a fixed lowfrequency (LF) and an antenna 210 modulated with two different centerfrequencies; wherein an impedance semiconductor circuit part 220inserted into said modulated antenna combines said two RF signals; andthe identification system further includes a transponder 200 having atank circuit to contain a resonant frequency equal to sum of twodifferent frequencies to re-radiate a data-tone carrier signal to suchcombined frequency and a narrow-bandwidth receiver 300 having areceiving antenna 310 to receive and demodulate said carrier signal byexcluding the transmitting RF signal and its harmonics to detect LFmodulating signal.
 2. The system according to claim 1, wherein thesystem detects a digital data signal overlapped by the narrow bandwidthreceiver 300 which is a means to start the digital stream preset toindicate the exist of the transponder 200 within the detection areawhenever the intensity and duration of the signal occurred in thetransponder 200 and detected by the narrow bandwidth receiver 300 exceedminimum values thereof.
 3. The system according to claim 1, wherein LFmodulation as one of the transmitted RF signals is a tone-modulated highfrequency (HF) wave f1 generated by the narrow bandwidth frequencymodulation, the other of the RF signals transmitting a continuous waveamong the fixed RFs.
 4. The system according to claim 3, wherein LFmodulation comprises the continuous tone-modulation RF signals and makesthose to be within a defined frequency range.
 5. The system according toclaim 1, wherein the transponder 200 comprises a charge pump circuit 230connected to a longitudinal part placed in a space surrounded by closeloop area faced each other to provide the tank circuit to tune with thesecond harmonics resonant frequency; and a dielectric folded dipoleantenna 210 and a non-linear impedance semiconductor circuit
 220. 6. Thesystem according to claim 5, wherein the non-linear impedance circuitconnects both sides of closed loop area at one end of the antenna inorder to form a tuning tank circuit having a frequency higher than theselected frequency by 2 limes as the resonant frequency thereof.
 7. Thesystem according to claim 1, wherein the narrow-bandwidth receiver 300comprises the receiving antenna 310 for carrier signal; a filter 311 toblock all signals other than the narrow-bandwidth signal generated atthe transponder resonant frequency; a demodulator detecting signal widthby comparing width of the filtered carrier signal and running thecomparison-determination output, detecting LF modulation only when saidcomparison-determination output exceeds the preset reference level andresponding dependent on the comparison-determination of a comparator312.
 8. The system according to claim 7, wherein the modulationdetection responds to LF modulation to activate the date stream outputfor minimum time after starting said LF modulation detection.
 9. Thesystem according to claim 7, wherein it includes a band pass filter 311to prevent signals except the one within the narrow-bandwidth receivedby the receiving antenna 310 and generated in the resonant circuit ofthe transponder, a series of means to produce intermediate frequency IFfor demodulating signals within the pass-band of said filter 311;alternative amplifiers 321,322 to compare and determine width of IF; anda narrow-bandwidth correction discriminator 323 to respond depending onthe comparison-determination output to demodulate said IF to allow thecomparator 312 to generate LF signal only when the width ofcomparison-output exceeds a pre-determined threshold.
 10. The systemaccording to claim 9, wherein LF modulation as one of RF signals withinnarrow RF deviation limits comprises a constant tone-modulation; thenarrow-bandwidth receiver 300 accepts a phase locked telecommunicationway by VCO 324 to tune with said constant tone frequency and activate anamplifier 340 connected to the output to allow digital data stream torun for a constant period.
 11. A system to detect cars or other objectsexisting within the detection area comprising a transmitter 100 to runand radiate radio frequencies (RFs) having a narrow-bandwidth by using acarrier frequency modulated by a certain LF tone; wherein the systemincludes a transponder 200 to respond the signal from the transmitter100 to be radiated by the transmitter 100 to run and re-radiate thecarrier signal by different harmonics; the re-radiated signal comprisinga fixed LF tone produced by adding a data stream to the LF tone; thesystem further comprises a receiving system 300 having anarrow-bandwidth filter 311 to contain the carrier signal re-radiated atsaid harmonics so that it produces filtered output corresponding there-radiation signal received by an antenna 310 to receive saidre-radiated carrier signal and to prevent the signals including ones ofeven the frequencies other than the narrow-bandwidth received by theantenna 310; and having a demodulation means responding to thecomparison level of the output to generate LF modulation signal anddemodulate the filtered output even when the comparator 312 exceeds thepreset threshold value and runs.
 12. The system according to claim 11,wherein the receiving system has a series of demodulating means torespond to the detection of LF modulation activating output for minimumtime after starting the monitoring of LF demodulation signal.
 13. Thesystem according to claim 11, wherein RF signal having narrow bandwidthcomprises a stable carrier modulated by a fixed audio-tone; said narrowbandwidth filter 311 includes a local oscillator 314, a mixer 319 todrive the intermediate frequency signal and a correction filter 324; aseries of means run by comparison-determination process within thepass-band for amplifying the intermediate signals to modulate the signalfrom the correction filter 324 detects width corresponding to the outputwidth from such correction filter 324; such multiple modulating meanscomprises a clamp circuit 325 responding to the comparison-determinationto fix the outputs from a narrow-bandwidth frequency discriminatingdevice and a correction discriminator 323 so that a fixed tonemodulation signal is generated during output process; and thecomparison-determination by the comparator 312 being excluded when thedetermined value exceeds the threshold value.
 14. The system accordingto claim 11, wherein the receiving system 300 includes severaldemodulating means to run the digital data stream output for a constantperiod and the digital code stream ranged of 64 bits to 16 kilobitsdependent on memory circuit attached within the passive transponder 200.